This invention relates to a color photographic element having improved image stability.
It is well known that yellowing, dye fade and thermal pinking are major concerns in the image stability of color prints. Over the years improvement in image stability has been achieved by introducing new couplers having a better resistance to dye fade and yellowing and also by introducing more efficient image stabilizers. However, in spite of this, the present level of stability is not considered satisfactory.
It has been known for a number of years that both fading of magenta and yellow image dyes and yellowing of residual magenta coupler are exacerbated by the presence of oxygen. This has led to the search for antioxidants and oxygen barriers. For example, Aono et al, in "The Effect of Oxygen Insulation on the Stability of Image Dyes of a Color Photographic Print and the Behavior of Alkylhydroquinones as Antioxidants" Journal of Applied Photographic Engineering, Volume 8, (1982) pp 227-231, indicate that improvements in dye fade and yellowing may be obtained by laminating a color print using polyethylene terephthalate. However, lamination is an expensive and laborious process.
Couplers are usually incorporated into photographic materials by dissolving the coupler in a high boiling organic solvent, optionally with a low boiling water immiscible auxiliary solvent, and then dispersing the resulting solution as an oil phase in an aqueous medium which generally contains a hydrophilic colloid, such as gelatin. Several recent patents suggest that improvements in image stability may be obtained by incorporating hydrophobic polymers in the oil phase of such dispersions. See for example, U.S. Pat. Nos. 4,710,454; 4,857,449; 5,001,045; 5,006,453; 5,043,255; 5,047,316; and 5,055,386. Many of these polymers have good oxygen insulating properties in the glassy state. However, the presence of high molecular weight polymers generally results in very high viscosities for the oil phase leading to large particle size and a subsequent decrease in dye density. The latter may be circumvented by using large amounts of a low boiling auxiliary solvent, such as ethyl acetate, which is then removed by evaporation, but this raises serious environmental concerns and adds additional expense.